Control system for a power plant having a primary and a stand-by prime mover



April 19, 1960 M GOTTLIEB 2,932,938

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INVENTOR MANIOUS GOTTLIEB cup valve in the closed position. the high pressure fluid is effective United States Fatent C CONTROL SYSTEM FOR A POWER PLANT HAV- 1316; a PRIMARY AND A STAND-BY PRIME Manious Gottlieb, Drexel Hill, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 26, 1958, Serial No. 757,287 3 Claims. (Cl. 60-6) and has for an object to provide an improved control system for automatically transferring control to the stand-by turbine, upon such failure.

In installations wherein the utmost reliability of the power plant is required, it is common practice to provide a primary prime mover (such as a turbine, internal combustion engine or an electric motor) for providing power, and a secondary prime mover to stand by, running at a low or idling speed, in readiness to assume the power requirementswithout interruption when required. In such installations, the stand-by prime mover is desirably a steam turbine equipped with a governor for controlling the speed of the turbine at a preselected or rated value when carrying the load;

It is another object of the invention to provide a con- .trol mechanism for overriding the turbine governor dur-.

ing stand-by conditions and maintaining the stand-by turbine at idling speeds, yet eitective to quickly and reliably transfer control to the governor, upon failure of the primary prime mover, thereby to bring the stand-by turbine up to the preselected speed without delay.

It is a further object to provide an override control mechanism for a hydraulic governing mechanism, Wherein' a cup valve is employed to regulate the pressure of hydraulic fluid delivered to the servomotor that positions .thesteam admission valve for the stand-by turbine.

In accordance with the invention, the stand-by steam turbine is provided with a steam admission valve structure'which, in the closed position, permits suflicient steam flow to drive the turbine at idling speed. The admission valve is regulated by a hydraulic fluid actuated system including a servomotor for positioning the valve and a hydraulic governor mechanism for regulating the pressure of hydraulic fluid delivered to the servomotor. The governor mechanism includes wall structure defining a high pressure fluid inlet, a controlled fluid pressure outlet communicating with the servomotor, and a drain outlet. A cup valve, movably positioned by a turbine speed sensing mechanism, serves to regulate the rate of flow of high pressure fluid through the drain outlet, thereby modifying the pressure of the controlled fluid in accordance with the speed of the turbine to maintain the turbine speed at a preselected rated value.

The control mechanism further includes wall structure providing a bypass passage communicating with the opposite face' of the cup valve, thereby to provide high pressure fluid to the cup valve effective to maintain the In the closed position, to maintain the servomotor in the steam valve closing position, thereby rendering the speed responsive mechanism ineifective to control the speed of the stand-by turbine.

I .An automatically actuated dump valve of the normally open type is further disposed in communication with the bypass passage, and is actuated to the open position by means responsive to failure of the primary prime mover to provide power to the load. Such means may comprise pressure responsive mechanism, speed responsive mechanism, voltage responsive mechanism (when the primary prime mover is an electric motor), or other suitable device. Accordingly, upon failure of the primary prime mover, the dump valve is opened, dumping the hydraulic fluid in the bypass passage to drain and freeing the cup valve. The cup valve thus opens and engages the speed sensing mechanism of the turbine, reducing the controlled fluid pressure to the servomotor, and causing the steam admission valve structure to open, thereby admitting steam to the turbine, as required to assume the load. Thereafter the turbine speed sensing mechanism is in full and sole control to maintain the turbine at the desired set speed.

The foregoing and other objects are eflected by the invention as will be apparent from the following de scription and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a schematic view illustrating a power plant installation having the invention incorporated therein;

Fig. 2 is an enlarged detail view, partially in section, illustrating the invention, the control mechanism being shown in one position;

Fig. 3' is a fragmentary view showing the control mechanism of Fig. 2 in another position; and

Fig. 4 is a sectionalview taken on line IVIV of Fig. 2.

Referring to the drawing in detail, in Fig. 1 there is shown a power plant installation comprising a primary prime mover, such as an electric motor 12, connected to a suitable electric supply by conductors 13 and drivingly connected to a primary feed water pump 14 for feeding water to 'a steam boiler (not shown) or other water utilizing apparatus, through conduits 15 and 16.

In parallel therewith, there is provided .a stand-by secondary prime mover 17 drivingly connected to a secondary feed Water pump 18 for providing water to the steam boiler through a branch conduit 19 and the conduit 16. The secondary prime mover is preferably a steam turbine and is connected to a suitable supply of steam (not shown) by a supply conduit 21. Steam flow to the turbine 17 is regulated by an admission valve structure 22, which, in turn, is controlled by a suitable hydraulic servomotor 24.

The conduits 15 and 19 are connected to a double check valve structure 25 comprising a first check valve member 26 for checking back flow of feed Water into conduit 19 when the pump 14 is running and a second check valve member 27 for checking back flow of feed Water into conduit 15 when the pump 3.8 is running.

In accordance With the invention, the servomotor 24 is controlled by pressurized hydraulic fluid delivered thereto by a control mechanism 29 cooperating with a speed responsive mechanism 30, driven by the turbine shaft 31. The control mechanism 29 is further connected by a conduit 32 to an automatic dump valve 33. As illustrated, the dump valve 33 is of the normally open solenoid type and is energized to the closed position by current flow through a pair of conductors 34 con nected to the motor supply conductors 13.

Referring to Fig. 2, the control mechanism 29 comprises a housing 36 including wall structure defining an inlet opening 37 for admission of pressurized hydraulic fluid from a suitable constant pressure supply source (not shown), a primary outlet 38 for delivering the fluid to the servomotor 24, and a main passage 39 connecting the inlet and outlet. The Wall structure further defines a drain outlet 40 connected to the main passage 3 9 by a port 41. Fluid flow through the, port, 41 is controlled by a regulating valve 42 of the cup type, slidably mounted in the housing 36 and having a central stem 43 extending downwardly therethrough. Fluid pressure in the main passage urges the cup valve in downward (opening) direction.

The main passage '39 further communicates with a bypass fluid passage 44 connected to the dump valve 33 by the conduit 32 and providing fluid pressure to the cup valve 42 in upward (closing) direction. Thus, with the cup valve 42 in the seated position, fluid flew through the drain outlet is blocked.

Immediately downstream of the inlet 37 an orifice 45 is provided for restricting flow to the bypass passage 44 and, in a similar manner, an orifice 46 is provided for restricting flow to the main passage 39.

The speed responsive mechanism 30 comprises a vertical shaft 47 rotatably connected to the turbine shaft 31 by a pair of helical gears 48 and having a plurality of 'flyweights 49 for vertically translating a centrally disposed collar Si), thereby to position the cup valve 42 in response to rotary speed of the turbine 17 and modify the pressure of the fluid admitted to the servomotor 24. As illustrated, the speed responsive mechanism 30 is effective to urge the cup valve upwardly with increase in turbine speed, thereby to increase the value of the fluid pressure signal to the servomotor. Conversely, with decrease in speed, the cup valve is permitted to move downwardly, thereby to decrease the value of the fluid pressure signal.

The'steam admission valve structure 22, as illustrated in Figs. 2 and 4, may be of the type shown in K. R. Stearns Patent No. 2,294,636, assigned to the assignee of the present invention, and comprises a tubular housing 51 defining a steam chest 52 connected to the steam supply conduit 21 and having a plurality of plug valves 53 for controlling steam flow into the turbine through passages 54. The plug valves are carried by a common actuator bar 55 which, in turn is carried by a pair of rods 56 extending upwardly through the housing 51 and connected to lever structure 57 as shown in Fig. 2.

The lever 57 is pivotally supported at '58 and is connected to the servomotor actuator rod 59 at one end and biased downwardly at the other end by a spring 60.

The admission valve structure has one notable difference with respect to the valve shown in the above mentioned Stearns patent. One of the plug valves, indicated as 53a, is disposed in the bar 55 above the level ofthe other valves, so that when the bar is in its lowermost position, as illustrated, all of the valves 53 close, with the exception of valve 53a. Accordingly, sufiicient steam flow is provided to motivate the turbine 17 at idling speed during the stand-by period, as will subsequently be described.

Operation During normal operation, the primary prime mover, motor 12, is energized to drive the pump 14, thereby supplying the required feedwater through conduit 15, check valve 27 and conduit 16 to satisfy the requirements of the steam boiler.

During such operation, the check valve 26 is urged to the closed position by the water pressure in the dual check valve structure 25.

In addition, the automatic dump valve 33 is energized to the closed position. Accordingly, as the hydraulic fluid in the'control mechanism 29 pressurizes the main passage '39, it exerts a pressure on the upper face of the cup valve 42 and urges the latter in opening direction. However, the bypass passage 44 is also pressurized by the same fluid confined therein and exerts a pressure on the lower face of the cup valve in closing direction. Since the lower face of the cup valve has a larger effective area than the" upper face, a net fluid force is exerted upwardly to move the cup valve upwardly, thereby blocking the port 41 and transmitting fluid pressure at full value to the and dumps the fluid in mean snar d- 1s sa d u d servomotor24. The servomotor, in turn moves its output shaft 59 upwardly to actuate the admission valve to the closed position, thereby reducing the steam flow rate to the turbine 1'7 to the low value which flows past the plug 53a. Accordingly, the steam turbine is operated at idle speed and is maintained in a warm state, ready to assume the feed water requirements of thesteam boiler, if required by failure of the primary prime mover to maintain such requirements.

During such operation, the speed responsive mechanism 36 is rotated well below its selected speed setting at idling speed. Consequently, its flyweights 49 are positioned-as illustrated in Fig. 2, with the collar 50 in a relatively low position. However, since the cup valve 42 is held away from the collar 50 in the port blocking position by fluid pressure in the bypass passageway 44, the speed sensing mechanism is ineffective to control the position of the cup valve.

In the event of electrical power failure in the motor supply conductors 13, the motor 12 will be deenergized and be incapable of driving the primary pump 14. Such power failure is quickly sensed by the suddenly deenergized dump valve 33 which moves to the open position the bypass passage 44 todrain, through the conduit 32.

As the fluid pressure in the bypass passage is relieved, the cup valve will drop until its stem 43 abuttingly ens gages the collar 50 of the speed sensing mechanism. The pressure of the fluid in the main passage 39 is quickly relieved by flow past the port 41 through the drain outlet 40 and the servomotor Wlll accordingly act in response to such reduced pressure signal to move the admission valve structure 22 in opening direction, as required, to quickly bring the turbine 17 up to rated speed. The secondary pump 18 is thus quickly brought into operation to provide the required feed water to the steam boiler through conduit 19. The water pressure in conduit 19 is effective to open check valve 26 and close check valve 27.

Thereafter, the cup valve 42 is controlled solely by the speed responsive mechanism 30 to regulate the fluid pressure in the control mechanism for actuating the servomotor 24, as required, to maintain the turbine speed at its required value. a

It will be noted that fluid drainage from the bypass passage 44 through the open dump valve 33 has substantially no adverse effect on the value of the controlled fluid pressure value, since such drainage is limited to a low value by the restricted orifice 45 disposed between the inlet and the bypass passage.

Although in the embodiment shown and described, the dump valve 33 is responsive to electrical power failure, it will now be seen that the invention is not limited thereto, and that the dump valve may be rendered responsive to any other suitable signal indicating failure of the primary'prime mover and its associated components to sustain the load requirements.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modificationswithout departing from the spirit thereof.

What is claimed is: 1

1. In a power plant installation wherein a primary prime mover is employed to provide power and a secondary prime mover is employed to stand by in readiness to provide said power in the event of failure of said primary ,prime mover to provide said power, a first valve for regul'ating motivating fluid flow to said secondary prime mover, a fluid actuated servomotor for positioning said valve, a control'mechanism for delivering fluid at variable pressure proportionate to the rotary speed of said i i said servomotor, said. control mechanism comprising wall structure defining a high pressure fluid inlet, a drain fluid outlet, a second valve interposed between said inlet andsaid drain outlet, conduit in et s: a d s smq sri means for positioning said second valve from a fully closed position to a fully opened position in response to speed of said second prime mover in a manner to regulate the flow of fluid through said drain outlet, whereby the pressure of said fluid in said conduit is modified in accordance with the speed of said secondary prime mover, a bypass passage connecting said fluid inlet to said second valve, whereby said second valve is restrained in the fully closed position by the high pressure fluid and said speed responsive means is rendered ineffective to control the position thereof, and a drain valve for venting said passage in response to a signal indicating failure of said primary mover to provide said power, said second valve being movable to an open position upon such venting and said speed sensing means being thereby rendered effective to control the movement thereof.

2. In a power plant installation wherein a primary prime mover is employed to provide power and a secondary prime mover comprising a turbine is employed to stand by in readiness to provide said power in the event of failure of said primary prime mover to provide said power; a first valve for regilating motivating fluid flow to said turbine; a fluid actuated servomotor for positioning said valve; a control mechanism for delivering fluid at variable pressure proportionate to the rotary speed of said turbine to said servomotor, said control mechanism comprising wall structure defining a high pressure fluid inlet, a primary fluid outlet, a drain fluid outlet, a second valve interposed between said inlet and said drain outlet and biased in opening direction by the high pressure fluid; said inlet and said primary outlet being in direct communication, conduit means connecting said primary outlet to said servomotor, means for urging said second valve toward the closed position in response to speed of said turbine in a manner to regulate the flow of fluid through said drain outlet, whereby the pressure of said fluid in said conduit is modified in accordance with the speed of said secondary prime mover, means including a bypass passage connecting said fluid inlet to said second valve, whereby to provide high pressure fluid for biasing said second valve to the closed position, said speed responsive means being thereby rendered ineflective to urge said second valve toward the open position, and a drain valve for venting the high pressure fluid in said bypass passage in response to a signal indicating failure of said primary prime mover to provide said power, thereby to permit said second valve to move to an open position upon such venting as determined by said speed sensing means and rendering said speed sensing means effective to assume control thereof.

3. In a power plant installation wherein a primary prime mover is employed to provide power and a secondary prime mover comprising a steam turbine is em ployed to stand by in readiness to provide said power in the event of failure of said primary prime mover to provide said power, a steam admission valve for regulating flow of steam to said steam turbine, at fluid actuated servomotor for positioning said valve, said steam valve permitting flow of steam to said turbine at a limited rate when in the closed position, whereby said turbine operates at idle speed when said valve is closed, a control mechanism for delivering fluid to said servomotor at variable pressure proportionate to the rotary speed of said turbine, said control mechanism comprising wall structure defining an inlet for high pressure fluid, a primary outlet for fluid at regulated pressure, a drain fluid outlet, a regulating valve disposed adjacent said drain outlet, conduit means connecting said primary outlet to said servomotor, means for urging said regulating valve toward the closed position in response to speed of said turbine in a manner to regulate the flow of fluid through said drain outlet, whereby the pressure of said fluid in said conduit is modified in accordance with the speed of said secondary prime mover, means including a bypass passage for providing high pressure fluid to said regulating valve in a manner to move the latter to the fully closed position, whereby said speed responsive means is rendered ineflectiveto control the position thereof, and a drain valve for venting said passage in response to a signal indicating failure of said primary prime mover to provide said power, said regulating valve being movable to an open position upon such venting as determined by said speed sensing means, and said speed sensing means being thereafter rendered effective to control thesmovement thereof.

Gieseler May 30, 1939 Hedman Aug. 31, 1943 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No... 2,932,938 April 19, 1960 Manious Gottlieb Column 4, line 5, after "plug" inser t valve column 5 line 13, after "primary" insert prlme Signed and sealed this 29th day of September 1960.

( SEAL) Attest:

KARL H, AXLINE ROBERT c. WATSON Attesting Oificer Commissioner Of Patents 

